Abstract
The successful drilling operation of oil and gas wells required high quality of drilling fluids which can stabilize well formations and able to withstand deep wellbore conditions of elevated temperature. Wellbore formations are mainly composed of shale (soft clay) and are likely to destabilize upon interacting with water. The instability of wellbore is caused by the interactions of water with the formation that results in the swelling of shale. Specialized drilling fluids can overcome this issue by stabilizing wellbore formations.
The purpose of this study is to develop a novel CNT-polymer nanocomposite through in situ polymerization process and to enhance rheological properties, borehole stability and filtration characteristics for high-temperature and high-pressure drilling applications. The thermal stability of nanocomposite was assessed using TGA analysis. The nanocomposite concentration (2 w/v.%) was employed with the base drilling fluid to study the impact on rheological properties at elevated temperature from 100°F to 300°F and 300 psi pressure. The results showed that rheological properties (viscosity, yield point, gel strength) were stable up to 300°F with (2 w/v.%) concentration of nanocomposite. The HTHP filtration experiment showed that fluid loss of modified drilling fluid significantly reduced compared to the base drilling fluid. Shale dispersion experiments were carried out at (100°F, 200°F, 300°F) for a shale sample obtained from the actual drilling field of Saudi Arabia. The XRD analysis of shale sample showed 19% clay contents in the shale sample. The shale recovery performance indicated that using 2 w/v.% concentration of nanocomposite in the base drilling (modified drilling fluid) has significantly reduced the dispersion of shale (up to 90%) compared to the base drilling fluid. The linear shale swelling experiments were carried out using nanocomposite modified drilling fluid and it was observed that use of nanocomposite appreciably reduced the swelling of shale compared to the base drilling fluid.
The use of polymer nanocomposite as water-based drilling fluid additive enhances the rheological properties, filtration characteristics and borehole stability at high-temperature drilling applications.
